Over the years, there has been developed a substantial body of patent and other literature directed to the formation and properties of poly(aryl ethers) (hereinafter called "PAE"). Some of the earliest work such as by Bonner, U.S. Pat. No. 3,065,205, involves the electrophilic aromatic substitution (e.g. Friedel-Crafts catalyzed) reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether. The evolution of this class to a much broader range of PAE's was achieved by Johnson et al., Journal of Polymer Science, A-1, vol. 5, 1967, pp. 2415-2427, Johnson et al., U.S. Pat. Nos. 4,108,837 and 4,175,175. Johnson et al. show that a very broad range of PAE can be formed by the nucleophilic aromatic substitution (condensation) reaction of an activated aromatic dihalide and an aromatic diol. By this method, Johnson et al. created a host of new PAE's including a broad class of poly(aryl ether ketones), hereinafter called "PAEK's".
In recent years, there has developed a growing interest in PAEKs as evidenced by Dahl, U.S. Pat. No. 3,953,400; Dahl et al., U.S. Pat. No. 3,956,240; Dahl, U.S. Pat. No. 4,247,682; Rose et al., U.S. Pat. No. 4,320,224; Maresca, U.S. Pat. No. 4,339,568; Atwood et al., Polymer, 1981, vol 22, August, pp. 1096-1103; Blundell et al., Polymer, 1983 vol. 24, August, pp. 953-958, Atwood et al., Polymer Preprints, 20, no. 1, April 1979, pp. 191-194; and Rueda et al., Polymer Communications, 1983, vol. 24, September, pp. 258-260. In early to mid-1970, Raychem Corp. commercially introduced a PAEK called STILAN.TM., a polymer whose acronym is PEK, each ether and keto group being separated by 1,4-phenylene units. In 1978, Imperial Chemical Industries PLC (ICI) commercialized a PAEK under the trademark Victrex PEEK. As PAEK is the acronym of poly(aryl ether ketone), PEEK is the acronym of poly(ether ether ketone) in which the 1,4-phenylene units in the structure are assumed.
Thus PAEKs are well known; they can be synthesized from a variety of starting materials; and they can be made with different melting temperatures and molecular weights. The PAEKs are crystalline, and as shown by the Dahl and Dahl et al. patents, supra, at sufficiently high molecular weights they can be tough, i.e., they exhibit high values (&gt;50 ft-lbs/in.sup.2) in the tensile impact test (ASTM D-1822). They have potential for a wide variety of uses, but because of the significant cost to manufacture them, they are expensive polymers. Their favorable properties class them in the upper bracket of engineering polymers.
PAEK's may be produced by the Friedel-Crafts catalyzed reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether as described in, for example, U.S. Pat. No. 3,065,205. These processes are generally inexpensive processes; however, the polymers produced by these processes have been stated by Dahl et al., supra, to be brittle and thermally unstable. The Dahl patents, supra, allegedly depict more expensive processes for making superior PAEK's by Friedel-Crafts catalysis. In contrast, PAEK's such as PEEK made by nucleophilic aromatic substitution reactions are produced from expensive starting fluoro monomers and thus would be classed as expensive polymers.
European Patent Application No. 125,816, filed Apr. 19, 1984, based for priority upon British Patent Application No. 8,313,110, filed May 12, 1983, is directed to a method for increasing the molecular weight by melt polymerization of a poly(aryl ether) such as PEEK.
The process of European Patent Application No. 125,816, provides a basis by melt polymerization above the crystalline melting point of the poly(aryl ether) to increase the molecular weight by chain extension of polymer blocks. The application theorizes that the procedure can be used for making the block copolymers described in U.S. Pat. Nos. 4,052,365 and 4,268,635. Implicit problems associated in the process of this application are the difficulty in controlling molecular weight of the resulting polymer and/or limiting isomerization and the problems associated with branching. The process of this European application would appear to be advantageous in making composites where the linearity and solution properties of the resulting polymer are not so critical.
PAEK block copolymers have been described in U.S. Pat. Nos. 4,052,365 and 4,268,635. U.S. Pat. No. 4,052,365 describes random or block copolymers having repeating units of the structure --Ar--O--Ar--CO and --Ar--O--Ar--SO.sub.2 --. The patent states that these block copolymers are crystalline. U.S. Pat. No. 4,268,635 describes a process for preparing polymers containing --Ar--O--Ar--SO.sub.2 -- and --Ar--O--Ar--CO-- units which the patentee believes to contain block structures. The patent states that the polymers are crystalline and exhibit improved high temperature properties compared with totally random copolymers of similar composition. However, the block copolymers in said patents require units with --SO.sub.2 -- linkages. The --SO.sub.2 -- linkage tends to break up the crystallinity of the polymer which results in inferior properties as compared to polymers which do not contain the --SO.sub.2 -- linkage but have ether and/or keto groups instead. Due to the amorphous nature of the sulfonyl containing component used in making these prior art block copolymers, lower rates of crystallization are induced and hence, their commercial utility is less than desirable. The --SO.sub.2 -- component so adversely affects the crystallinity properties that there is a maximum limit in the T.sub.m, far below that for the block polymers suitable for use in this invention. A further deficiency of these prior art block copolymers is that they cannot be used to form compatible blends with other PAEKs.
The use of reinforcing fibers and whiskers as reinforcements in plastics is also well known. See generally Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, Wiley-Interscience, Volume 13, pages 968-978, which notes that glass fibers are the usual reinforcement in thermoplastics, although the use of graphite fibers is growing.
The use of silicon carbide whiskers in various matrix materials ranging from glass to metals is known as disclosed in U.S. Pat. No. 4,463,058 to Hood et al. The use of silicon carbide in a variety of plastics has also been documented widely in the patent literature. Thus U.S. Pat. No. 4,252,692 to Taylor et al. discloses polymer compositions containing silicon carbide which exhibit non-linear electrical resistance characteristics and which are useful as heat-shrinkable materials; U.S. Pat. No. 4,144,207 to Ohnsorg discloses injection moldable and sinterable ceramic materials made by coating a ceramic material such as silicon carbide with a mixture of thermoplastic resin and oils or waxes; U.S. Pat. No. 3,920,605 to Sato et al. discloses filler reinforced coordination bonded metal compounds containing acrylonitrile and/or methacrylonitrile copolymers, wherein silicon carbide whiskers represent one among many inorganic fillers which may be used; U.S. Pat. No. 3,386,840 to Gruber discloses fibrous beta crystalline silicon carbide and reinforced shaped objects made from silicon carbide fibers and a continuous medium, including polymerized organic monomers; U.S. Pat. No. 4,111,891 to Reynolds, Jr. discloses a friction material useful in railroad disc brakes which contains silicon carbide as a friction material; British patent specification No. 1251641 to Hollingsworth et al. discloses reinforcing numerous thermoplastics with a variety of reinforcing fibers, including silicon carbide, the fibers having certain minimum mean values of tensile strength and Young's modulus and closely similar aspect ratios.
Several scientific journal articles have been published which review the properties of polymeric composites reinforced with silicon carbide whiskers or containing silicon carbide particles. The articles generally disclose applications of silicon carbide which call into play its good thermal and mechanical properties, although its ability to function in a composite as an electric insulator is also noted. Many articles cite epoxy based resin systems as a prototype, see for example Strife et al, J. Mat. Sci., 17, 65-72 (1982); Ishikawa et al, New Mat. & New Proc., 1, 36-42 (1981); Teranishi et al., Ext. Abstr. Program--Bienn. Conf. 16th, 620-621, (1983); and Garcia, Methods of Improving The Matrix Dominated Performance of Composite, Structures: A Technical Review, Naval Air Systems Command Report No. NADC-83058-60, July, (1983).
Blumberg in J. Ind. Fab., 1, 38-52 (1982) reviewed the properties and potential applications of high-modulus fibers including aramid fibers, carbon fibers, and silicon carbide fibers. The high thermal stability of silicon carbide beyond that required for even the most heat-resistant resin systems (e.g. polyimides) is noted. Blumberg concludes that a natural consequence of such high thermal stability would be to use silicon carbide in high temperature matrixes such as metals and ceramics.
Negishi et al., Rev. Elec. Comm. Lab., 29, 58-65 (January-February 1981) disclose the use of silicon carbide particles to increase the abrasion resistance of PVC submarine cable coverings.